Cyclic aminobenzaldehydeacetals of



Patented Sept. 6, 1949 2,481,434 YCLIC AMINOBENZALDEHYDE AcErrALs or 1,22 AND IB-GEYCOLS CARBON ATOMS David, M.

Wilmington,

Nemours & Company,

poration of Delaware OF TWO TO FOUR- McQueen. and David W. Woodward, Del., assignors to E. 1. du Pont de- Wilmington, Del, a cor-- No Drawing. Application December 28, 1946, Serial No. 719,110

6 Claims. i

This invention. relates to cyclic aminobenzaldehyde acetals of 1,2- and 1,3-glycols and to their preparation.

An object of this invention is to provide a new class of organic compounds. Another object is to provide a new class of aminobenzaldehyde acetals which are useful in the preparation of polymeric color formers, A. further object is to provide new intermediates which can be used to prepare polyvinyl acetal color formers in a more eificient manner. Still other objects will appear from the following description of the invention.

The novel cyclic aminobenzaldehycle acetals of 1,2- and. 1,3-glycols of 2. to 4v carbon atoms of this invention can be advantageously prepared by catalytically reducing the corresponding cyclic acetals of nitrobenzaldehydes with hydrogen at elevated temperatures and pressures, e. g., 50to 100 C. and 100 to 2000 pounds per square inch. The resulting aminobenzaldehyde acetals are then recovered in a pure. state by distillation under reduced pressure in the presence of at least 0.0025 mol equivalent of a. non-volatile alkali.

The cyclic nitrobenzaldehyde acetals just described which are used in the preparation of the cyclic aminobenzaldehyde acetals can be made by reacting a nitrobenzaldehyde with a 1,2- or 1,3-g1ycol of. 2 to 4 carbon atoms under. acetalforming conditions. This. maybe accomplished by acetalization of a nitrobenzaldehyde by removal of water from an acid catalyzed mixture of a nitrobenzaldehyde, 1,2-ethylene glycol or 13- propylene glycol, etc. and. a water-immiscible, high-boiling liquid, e. g., benzene, toluene, xylene, chlorobenzene, etc., as a water-entrainin solvent. Suitable catalysts include phosphoric, suliuric, hydrochloric, and p-toluene-sulfonic acids.

The invention is not linnted to the: unsubstituted cyclic aminobenzaldehyde acetals. of 1,2- and 1,3-glycols oi 2 to 4 carbon atoms. On the contrary, the benzene nucleus may be substituted by monovalent hydrocarbon (R) radicals or hydrocarbon ether (RO-) radicals, e. g., methyl, ethyl, phenyl, naphthyl; methoxy, ethoxy, etc. The lower alkyl and alkyl ether substituted derivatives are the most important. The compounds are normally prepared from the corresponding nitrobenzaldehydes. While any nitrobenzaldehyde, e. g., the ortho, meta, or para isomers. be used in the preparation of the. cyclic metals I ture.

it is preferred to use metasnitrobenzaldehydesbecause, (1) they are readily available by, nitration of benzaldehydes, (2). they aremore stable and formv more stable derivatives than do the. ortho isomers, and (3)- their' acetals give better yields onreduction than do theortho, and-para isomers.

Catalytic reduction oi the nitrobenzaldehydc acetals is best accomplished; by rapid. agitation of a suspension of. the. catalyst in the nitro body in the presence of hydrogen at pressures below 2000 pounds per square inch. and at temperatures in the. range of. to 100C. and preferably between and..90 h? hydrogenation reaction is continneduxrtil: the nitrogroun is reduced to an. amino group. It is important the temperature. be maintained in this r gion since-at higher ten-n3;email-sires hydrogenolysis of the group occurs and. instead: of acetals oi amine benzaldehydes the products are toluidines. At temperatures below 50 C the reaction is extremely slow or fails to so at all, As an. aid, in controlling the. temperature and; moderatingthe reaction, solvent 11.61}. as others, and hydrocarbons, maybe added to the-reaction mi The catalysts are preferably used-. inthe ratio oi between 1 and 10. parts per parts of the nitroacetals. The completion of the 129:- ductionof; th nitrogroupis marked by a sudden decrease in the rate. of absorption of hydrogen. At. this point, the reac ion mixture cooled and the pressure. releasedto present further reaction.

The ac talsof aminobem dehrd s smea d by theabove reduction method are. of good. quality but are unstable, espflcially when heated. It has been ioundth it they may be heated for prolonged periods, or distilled wi ihflll d compos ti n if they are stabilized by the addition of, a non.- volatile alkali. The minimum. amount:- of; alkali is at least 0.0025 mol equivalent per mol of aminoacetal and it is preferred that at least 0.005 mol equivalent be used. With this amount of stabilizer, no appreciable decomposition occurs even when the mixture is heated to C. for several hours. Larger amounts, for example, up to 0.025

-' mol equivalent or more can. of o rse, be use while with smaller amounts decomposition will; occur. The decomposition. occurs through. loss or alcohol with resultant formation. of an aldehyde-- amine resin. Many nonvolatile alkalis may be used. T1185 inch-fie the alkali metal hydroxides,

Into a stainless steel reactionyessel equipped.

means for agi-i for cooling and heating, having 7 tation, and fitted for vacuumdistillation are charged 86 parts of recrystallized m-r'iitrobenz' aldehyde having a melting range of 55-57, 38.3 a

parts of ethylene glycol, 86 parts of xylene, and

0.17 part of phosphoric acid. The vessel is closed and heated, with agitation, rapidly to 120, then more slowly to 160. During this time about 10 parts of water and 56 parts of xylene areremoved by distillation. Heating. is discontinued and the internalpressure gradually reduced to 100 mm.

to remove the residual water and xylene. Tothe residue'in thekettle are added 100 parts'of ethanol and 0.105 part of sodium hydroxide. The

-follows: 131/0.4 mm. 138/1.10 mm., 142'/1.5

mm., 145/2.0 mm., and 158/6.0 mm. Physical constants determined for this compound are:

n-l.l99 M -Found: 45.75; calculated 45.64:

I Example II Using an equal weightof p-nitrobenzaldehyde in the procedure of Example I, a 90% yield .of

.; p-nitrobenzaldehyde;ethylene glycol acetal having a melting point of 89-90 C. is obtained.

This in turn is hydrogenated and distilled by the procedure of said example to yield p-aminobenzaldehyde ethylene glycol acetal having a boil-' ing point of 150 at 1 mm. and the formula:

temperature is adjusted to 70 and the solution filtered into a stainless steel crystallizing vessel. -While agitating-the solution, its temperature is plete, the mixture isj filtered and 'air-driedt'o yleldl05 parts (95% based on the nitroaldehyde) 7 'of m-nitrobenzaldehyde"ethylene glycol acet'al having a melting range of 56-'58.'

A hotsolution of-134 parts of the above niadju'sted to 50. After sweeping out the air with hydrogen, the hydrogen-pressure is increased" to 300'pounds and agitation' started. The tempera- Analysis: calculated, for *Cal-IuOzN: C =65.5

. V a Example III r Ina reaction vessel fitted with a short'distilla tion column is placed l51'part's of m-nitrobenzaldehyde, 150' parts of xylene; 1 part of 5%;phosloWer'edto 5 a'nd, after crystallization is com- 1 t'roac'etal and? parts of' a nickel-on-kieselguhr catalyst in 134'parts of methanol is charged to i a hydrogenation autoclave and the temperature ture rises to 80 and is held 'there'bycooling.

Thereductionis carried out at a hydrogen pres sure of300 to 500 pounds per square inch. The

rapid absorption of hydrogenfalls ofi' sharply after the theoretical amount requiredto reduce the nitro group'has been used. At this point the reduction is stoppedby, cooling to 40 and releasing the hydrogen pressure. The charge is filtered and 0.42 part of sodium hydroxide is added. This stabilized, alcoholic solution of m-aminobenzaldehyde ethylene glycol acetal is placed in a stainless'*steel still "having a porcelain ringpacked column. The charge is'heated to distill methanol until the internal temperature reaches 100, at which-point vacuum is applied until the internal pressure is reduced to-5 mm. The temperatureis then increased slowly until distillation occurs. The product, m-aminobenzaldehyde ethylene glycol acetal, boils in the range of 155- 160 0. at 5 mm. and has the formula:

V V O-CHz 'NHP I V F The total-yield is 103 parts or 91% based'on the nitroacetal. vAnalysis shows 'a' composition of 0:66.10, 66.27; Hf 6.56,' 6.53; N='8.08,,7.96 as compared with a'ca'lculated value f0r 'C9H11O2N' of C=65.50.%; I-I' =6.56%; and N=8:.5. Additional boiling points'of this compound are as phoric acid, and 84parts of trimethylene glycol. The mixture is stirred and heated untilno dis-'- tillation occurs at an internal temperature of 150, then the pressure is reduced until n distillation occurs at a pressure of 50 mm; and. a temperature of 110. The mixture is added to '320 parts ofethanol containing 2 parts of sodium hydroxide and filtered at 60. V yellowcrystals are formed which when dried melt at'5860.= Analysis: J N=6.7; found:N=6.9. I This acetal isreduced to the corresponding amino acetal and distilled as in Example I to give a yield of m-aminobenzaldehyde trimethylene' glycol acetal, a low-' melting solidwith a melting point of 73 .150 76; a boiling point of141 at, 1.5 mm.and a rormmaz; 1

' OI-CH:

NHr-

Example V i Following the procedure of'Example I and replacing the b-nitrobenzaldehyde with 103 parts of 3-nitro-4-"nethoxy-benzaldehyde, the corresponding ethylene glycol acetal melting-at48-'- 53 is obtained. Analysisi calculated for C10H11O5N: N=6.23; found: N=6.54. Following the reduction and distillationprocedureof Example I, a 90% yield fof 3' -aminomethoxybenzaldehyde ethylene glycol acetal 173 at 5 mm. and 146 at 1 mm. and the formulaz' is obtained. Analysis: calculated for Ci HizOgNi N= ,8;. found: ,c=s1,49;. H=6' ;N=7. '1. I

' On cooling, pale calculated for C'1oI-Ii1O4N: V

boiling at Example V Following the procedure of Example I using 94 parts of 3-nitro- -tolualdehyde in place oi the m-nitrobenzaldehyde, there is obtained in 95% yield the corresponding acetal melting at 44". Analysis: calculated for CioH'nOaN: N=6.l; found: N=6.9.. On reduction and distillation according to the procedure of Example I, there is obtained an 84% yield of 3z-amino-4-methylbenzaldehyde ethylene glycol-acetal boiling at 161 at 5 mm. and having the formula:

Example VI To 165 parts of the acetal of Example I is added 0.2 parts of sodium hydroxide and the mixture heated to 150 C. The vapor pressure remains unchanged at. 3.]. mm. during a period of six hours. In a similar experiment, omitting the sodium hydroxide, the vaporpressure begins to rise after a very short period: because oil the formation of ethylene glycol.

Although the above methods have been found to bev the most practical from. ease of operation and yield, other methods may-be used for accomplishing thesesteps. For instance, the acetalization may be carried out bysaturating a solution of the nitrobenzaldehyde in the glycol with hydrogen chloride, allowing it to stand forseveral days, then neutralizing the acid, washing out the excess glycol, and recrystallizing the crude product. Another method involves reaction of the nitroaldehyde with the cyclic sulfite of ethylene glycol (CH2O)2SO. Also, the dimethyl acetal may be prepared from the nitrobenzaldehyde and methanol or dimethyl sulfite and the resulting dimethyl acetal heated with a glycol in the presence of an acid catalyst to effect acetal interchange. The reduction may be carried out by chemical means, e. g., with sodium or ammonium sulfides or by sodium in alcohol, etc. Although some purification of the final product can be obtained through solvent extracts and washings, the ready distillability of the product makes rectification the simplest and most useful method of purification.

Other acetals that may be prepared by this method include those .of the following glycols: 1,2-propylene glycol; 12- or 1,3-butylene glycol. Other hydrogenation catalysts that may be used in the reduction can be prepared from ruthenium oxide, palladium, platinum, cobalt, copper chromite, cobalt sulfide, etc. The catalysts may be supported on inert carriers. Other diluents that may be added to the reduction mixture include ethanol, propanol, benzene, toluene, hexane, etc. The reduction is preferably carried out as rapidly as can be done at temperatures below 90 C. Since the reaction is exothermic, this requires efiicient agitation and cooling.

Other stabilizers that can be used to prevent the heat decomposition .of these acetals include the following: hydroxides, carbonates, oxides, amides, and alkoxides of lithium, sodium and potassium; oxides and hydroxides of calcium, barium, or any other alkaline, inorganic salt of the 1st or 2nd group of the periodic system which forms an aqueous. solution havinga pH. greater than 10. Also useful are nitrogen compounds of the tertiary, i. e., R3N,.or quaternary, i. e., RANCH, classes which form aqueous solutions having a pH of 10 or greater and which: are stable and nonvolatile under the distillation conditions used, i. e., temperatures in the range of to 200? C. and pressm'es of less than 10' mm. B in the formulae maybe an alkyl group, such as dodecyl or hexadecyl, or'an aralkylgroup, such as benzyl.

One .of the most important uses of the cyclic aminobenzaldehyde acetals of L2- and 1,3-glycols of 2 to 4 carbon atoms is in the preparation of color-forming. polyvinyl acetals, especially those diflicult to obtain by other methods. Thus, the large class of color formers. containing aldehyde reactive groups, i. e., reactive methylene groups, can now be converted to color-forming polyvinyl acetals by use .of these new compounds in which the aldehyde group is continually protected from condensation with the dyev coupling reactive group. of the. color former by the: acetal: grouping; However, the resulting color former readily ermdenses with polyvinyl alcohol through acetal interchange. Among such active; methylene color formers which cannowbe converted to polyvinyl acetals are the ('1) beta-ketoacylamides of the type RC'OCHZCONHR, where R. is a hydrocarbon or heterocyclic radical and R is preferably aromatic, e. g., benzoylacetanilide, stearoylacetanilide, p-acetoa'cetam-inobenzoic acid; (2) pyrazolcnes, e. g., .kp-carboxyphenyl-S-methyl- S-pyrazolona. 1'-phenyl-3-carboxy-5-pyrazolone; (3-) benzyl cyanides; 1)- indoxy-ls and thioindoxyls; (5) homophthalimides: (6). 2,4-dihydroxyquinoline; (7") diketohydrindene; (8.): malionamides; (9) phenacylpyridinium halides; (10) hydroxypyridine, etc.

The novel acetals also are valuable for use in preparing dyes for general dye purposes, such as, for textiles, plastics, pigments, etc., or any application where an aldehyde group increases the fastness by reason of its reaction with a high molecular Weight component or fiber. Thus, azo dyes may be prepared by diazotization of maminobenzaldehyde acetals and coupling with an azo dye-coupled component or preformed aZo dye, or the dye may be joined to a m-aminobenzaldehyde acetal through an amide or sulfonamide group. Such dyes are particularly useful with fibers containing hydroxyl, amino, or amide groups with which the acetal group may react under properly controlled conditions. Dyes of this type are exceptionally fast to washing.

As many widely different embodiments of this invention can be made without departing from the spirit and scope thereof, it is to be understood that the invention is not to be limited except as defined by the claims.

What is claimed is:

1. The cyclic aminobenzaldehyde acetals of the formula:

where R is a member taken from the group consisting of hydrogen, methyl, ethyl, phenyl, naphthyl, methoxy, and ethoxy groups, R is taken from the group consisting of hydrogen and methyl, and n is a cardinal number from 0 to 1.

2. The cyclic acetal of the formula:

' -011: NH: 011 V O H: C1130 -3. The cyclic acetal of the formula:

V OCH:

NHP

4. The cyclic acetal of the formula:

5. The process which comprises catalytically reducing cyclic nitrobenzaldehyde acetals of the formula:

where R is a member taken from the group consisting of hydrogen, methyl, ethyl, phenyl, naphthyl, methoxyyand ethoxy groups, R. is taken from the group consisting of hydrogen and methyl, and-n is a cardinal number from 0 to 1 with hydrogen until a cyclic aminobenzaldehyde acetal of an alkyleife glycol'of 2 to 4 carbon atoms is formed and recovering the latter acetal.

6. The process which comprises catalytically reducing a cyclic nitrobenzaldehyde acetal of the formula: s

No, I o-c zrm' GH cm).

O-CH:

acetal. 7

DAVID M. MCQUEEN. DAVID W. WOODWARD.

, REFERENCES CITEDE The following references are of record in the file of this patent: V

UNITED STATES PATENTS Number Name Date 2,272,153 Moyle Feb. 3, 1942 2,415,021 Morey Jan. 28, 1947 OTHER REFERENCES I I Chemical Abstracts, vol. 23, 596, 597 (1929) i Certificate of Correction Patent No. 2,481,434 September 6, 1949 DAVID M. MCQUEEN ET AL. It i he b e tifi d that errors appear in the printed specification of the above numbered patent requiring CQ as W I C l 3, li 74, f 8,5 read 8.5%; column 4, line 59, for b-nitrobenzaldeh d d a it b ld h d column 7, lines 16 to 19, for that portion of the formula reading and that thvsfl lfl Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 28th day of February, A. D. 1950.

THOMAS F. MURPHY,

Assistant Gammz'saioner of Patents. 

